The physical and mechanical properties of polyurethane foams make them useful for a wide variety of applications, including thermal and sound insulation, upholstery and bedding. However, many foams, including polyurethane foams, are inherently flammable and lead to the melting and spread of burning debris. In the case of such “conventional” foams this can lead to sustaining combustion by progressive smoldering even after the actual flames have extinguished.
It is considered that cellular materials manufactured from flammable polymers are more flammable than the solid materials because the insulating effect of their cellular nature allows a rapid build-up of heat at the heated surface with a consequence high rate of pyrolysis. In solid materials this heat build-up is at a lower rate because of the higher conductivity of the solid material. Although rigid foams have similar thermal conductivity behavior as flexible foams, the high crosslinked nature of their chemical structure makes them less flammable as polymers and also inherently more inclined to form a protective char rather than to form the flaming molten polymer droplets which occur with flexible foams. While both solid and rigid cellular materials burn less easily than flexible foams and are easier to extinguish, they all tend to smolder and emit toxic fumes.
Accordingly, in light of the above, certain applications to date have remained a difficult challenge for the application of polymer foams. One such area is foam insulation for building applications. Due to the fact that all foam building products are required to meet specific fire performance standards required by U.S. building codes, it has not been possible for polymer foam insulation without thick fire-resistant protective surfaces, such as one-half inch gypsum board, applied over the foam insulation to meet such codes.
As such, there is a need in the art for polyurethane foam insulation products that are designed to meet one or more U.S. building codes when utilized as a stand-alone product, or even when covered with a thin coating or surface finishing product, in order to lower the installed costs of such products.